A construction company director was warned he would struggle to get work in Canberra unless his workers were union members.

The royal commission into trade union corruption has heard the CFMEU's ACT assistant secretary, Jason O'Mara, and organiser Tony Vitler told the director they would actively promote his company in Canberra if his workers joined the union.

HD Projects director Clyde Daish told the hearing the men sought a meeting with him in February 2012 and told him they had significant influence over the Canberra construction market.

"As a result of their influence, unless I had my boys joined up as members, I would struggle to win any work in Canberra," Mr Daish said.

He asked his staff to join so the union would put in a good word for the company, but payments were stopped in recent months after he gave up hope of winning any work in Canberra.

Mr Daish said he was forced in 2010 to pay the CFMEU $3674.20 in membership fees for 12 "ghost" employees who did not exist after CFMEU officials disrupted his worksite for half a day.

He had between six and eight staff working on the site at the time and all or most were members of the CFMEU in NSW.

But when he tried to explain that to union organiser Halafihi Kivalu, he was told: "You need to pay anyway. I'll just make up 12 names."

Mr Daish said he had never before encountered such a disturbance on a worksite or been asked for memberships of workers who were already members.

He says no membership forms were filled out for the 12 "ghost" members.

"It was invented, from what I understand, just to get that portion of money into the ACT branch," he said.

He agreed to pay because the worksite had come to a halt and it seemed "a fairly easy way" to move forward.

He later received an invoice for the payment printed on CFMEU letterhead.

The CFMEU later asked the company to renew the memberships but Mr Daish refused because he could not identify any of the names on the list.